Stimulant action of thyrotropin-releasing hormone on ciliary nerve activity

Thyrotropin-releasing hormone (TRH) was found to cause a dose-dependent stimulation of tonic ciliary nerve activity when administered intravenously to chloralose anesthetized cats. This increase in nerve activity appeared to be independent of the excitatory light reflex. TRH also produced a dose-dependent pressor effect in these preparations. These findings suggest that TRH may play a role as a neurotransmitter or neuromodulator with regard to central parasympathetic outflow to the eye.